Developer conveying apparatus

ABSTRACT

The developer conveying apparatus comprises a drum and magnet assembly for conveying developer material to the photoconductor surface of an electrophotographic printer. The drum is mounted for rotation on an axis at a right angle to the photoconductor drum. The magnet assembly is mounted in close proximity radially to the carousel drum to produce a magnetic field pattern parallel to the rotational direction of the drum. The developer material is moved into the magnetic field as the carousel drum is rotated so that the developer material adheres to the inner surface of the drum and is conveyed to an inclined chute located within the upper portion of the drum. The developer material moves beyond the magnetic field and drops to the inclined chute. The material cascades down the chute and enters a development zone where it passes through a restricted path between a development electrode and a photoconductor to develop the electrostatic images on the photoconductor. The developer material then returns to the bottom of the carousel drum where it is enriched with toner and the cycle is repeated as long as image development is required.

[56] References Cited UNITED STATES PATENTS 2,761,416 9/1956 Carlson ..118/51 2,892,445 6/1959 Giaimo, Jr ..113/637 2,919,674 1/1960 Sih ..118/637 3,122,454 2/1964 Grimm et a1 ..118/637 3,122,455 2/1964 Grimm et a1 "118/637 3,635,553 1/1972 Adamek ..355/3 3,648,657 5/1972 Rueckwald.... 18/637 3,661,118 5/1972 Royka ..118/636 3,641,977 2/1972 Hudson ..118/637 CONTROL M25 MEANS 0 United States Patent 1 [in 3,712,266

Stauiier 51 Jan. 23, 1973 1 DEVELOPER CONVEYING Primary Examiner-Mervin Stein APPARATUS Assistant ExaminerLeo Millstein [75] lnventor: Russell A. Stauil'er, San Jose, Calif. An0mey otto Schmld et [73] Assignee: International Business Machines [57] ABSTRACT Corporation, Armonk, N.Y. The developer conveying apparatus comprises a drum 1 1 Filedi g- 27, 1971 and magnet assembly for conveying developer materi- [21] Appl. No.: 173,516 al to the photoconductor surface of an electrophotographic printer. The drum is mounted for rotation on an axis at a right angle to the photoconductor drum. [52] US. Cl. ..118/636, 117/175, 118/7, The magnet assembly, mounted 1 close proximity 118/637 HB/DIG- 222/D1G- 1 radially to the carousel drum to produce a magnetic [51] hit. Cl. ..G03g 13/00 field pattern parallel to the rotational direction of the [58] Field of Search.....1 18/312, 636, 637, 7, 8, DIG.

drum. The developer material is moved into the magnetic field as the carousel drum is rotated so that the developer material adheres to the inner surface of the drum and is conveyed to an inclined chute located within the upper portion of the drum. The developer material moves beyond the magnetic field and drops to the inclined chute. The material cascades down the chute and enters a development zone where it passes through a restricted path between a development electrode and a photoconductor to develop the electrostatic images on the photoconductor. The developer material then returns to the bottom of the carousel drum where it is enriched with toner and the cycle is repeated as long as image development is required.

12 Claims, 8 Drawing Figures PATENTEDJAH 23 I973 SHEET 1 OF 2 filD-v l 'FIG.3

ZNVENTOZ? RUSSELL A. STAUFFER BY wi 'j PATENTEU JAN 2 3 I973 SHEEI 2 OF 2 FIG.5

FIG.8

DEVELOPER CONVEYING APPARATUS BACKGROUND OF THE INVENTION This invention relates to material conveying apparatus and more particularly to improved apparatus for conveying developer material to a photoconductor surface in an electrostatic printer.

Developing apparatus which utilizes a bucket type conveyor has been successfully used in prior art photographic imaging systems. However, a high speed electrophotographic printer has operational requirements that cannot be provided by the bucket type of conveyor. At the developer flow rates required for an electrophotographic printer, the bucket type conveyors produce substantial wear on the developer materials and also the conveying apparatus. It is therefore an object of this invention to provide a developer conveying apparatus which produces a more even flow at a high developer flow rate.

It is another object of this invention to provide developer conveying apparatus which produces continuous cross-mixing of the developer to produce consistently dense images.

It is a further object of this invention to provide developer conveying apparatus in which the distribution of the developer flow across the photoconductor surface can be easily controlled on a selective basis.

SUMMARY OF THE INVENTION Briefly, according to the invention, there is provided developer conveying apparatus comprising a drum member mounted for rotation about an axis substantially perpendicular to the electrophotographic surface, means for producing a magnetic field directed circumferentially along a predetermined portion of the drum member so that the developer material is conveyed in an upward direction by rotation of the drum member and a chute member mounted at an angle to the electrophotographic surface is provided for directing the developer material to the surface as the material is conveyed out of the magnetic field.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of the printer embodying the invention showing some parts of the developer conveyor apparatus cut away;

FIG. 2 is a side view of the developer conveying apparatus of FIG. 1 showing some parts cut away;

FIG. 3 shows a view of a preferred embodiment of the magnetic field producing means;

FIG. 4 is a section view of the apparatus shown in FIG. 3;

FIG. 5 is a top view of an alternate embodiment of the developer conveying apparatus;

FIG. 6 is a front view partially in section of an alternate embodiment of the developer conveying apparatus which shows a selectively actuable developer gating means;

FIG. 7 is a section view along the lines 7-7 of FIG. 6 showing the gating means closed;

FIG. 8 is a section view along the lines 7-7 of FIG. 6 showing the gating means open.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, the relationship between the developer feeding apparatus and a typical electrostatic printer is shown schematically in FIGS. 1 and 2. In this apparatus a rotatable drum 10 carries around its periphery an electrophotographic photoconductive member 12 on which is directed an image which it is desired to reproduce on a recording sheet. The surface of the photoconductor is uniformly charged to a predetermined polarity by suitable means such as a corona discharge device 11, and a suitable exposure means such as a cathode ray tube 15, is operable to direct the image to be copied onto the surface of the photoconductor, thereby producing a charged pattern in the form of the image to be copied. Thereafter the drum passes a development station 14 at which a developer mixture is cascaded across the electrostatic image on the surface of the photoconductor 12 as is known in the art. The toner which has charge opposite from the polarity of the electrostatic image charge is attracted to the drum surface to render the image visible, whereas excess toner and all of the carrier in the developer continues to cascade downwardly into the reservoir 16. A copy paper 19 is fed into contact with the developed electrostatic image and the toner is attracted to the sheet by suitable means such as a corona discharge device 21 having a polarity opposite that of the toner, thereby attracting the toner to the copy sheet. The sheet is separated from the drum and fed past a fusing station 23 which serves to fuse and permanently fix the toner to the paper. Since transfer of all the image toner is not usually accomplished, the residual toner is cleaned from the surface of the photoconductor by a suitable cleaning apparatus such as cleaning brush 17. This operation completes the cycling of the drum for reproducing the desired image.

The developer apparatus according to the invention, uses a two-component developer material to effect image development. One developer component commonly known as carrier comprises granular beads formed of a ferromagnetic material coated with a suitable material. The other developer component comprises a finely divided pigmented powder material commonly known as toner. The toner and carrier materials are tribo-electrically charged to opposite polarities due to the characteristics of the material used. When the toner and carrier are brought into rubbing contact, an electrostatic charge in generated between the two materials and the toner material adheres to the carrier in a charged state. As the toner laden carrier beads move in contact with the photoconductive surface, the toner is electrostatically stripped from the carrier and attracted into the image areas by the relatively strong latent electrostatic image force fields.

In accordance with the present invention, the developer apparatus maintains the proper balance between the quantity of electroscopic toner and the carrier in the electrophotographic developer so that uniform quality copies result. This is accomplished by continuously replacing the quantity of toner which goes to make up the imprint on the printed record. The developer apparatus comprises a carousel drum conveyor I8 which functions to continually recirculate the developer material from the reservoir portion 16 to chute member 2th which serves to direct the developer material over the drum surface for development of the electrostatic image. The inner surface of the periphery of drum lltl has a frictional surface so that developer material is engaged from the reservoir portion 16 and conveyed to the top of the drum at which time gravity causes the developer material to cascade across chute 2t) and thence across the surface of the drum to develop the image. A small quantity of the developer material cascading across chute 26) is directed to the toner concentration sensor means 2%. Sensor means 29 produces an electrical signal on line 21 proportional to the percentage of toner present in the developer material. A toner feed apparatus 22 is provided to replenish the toner utilized from the developer material during the printing operation in response to a signal generated by control means 25.

Control means 25 may comprise any suitable device for supplying electrical control signals to perform the desired printing functions. Control means 25 may comprise the processor of an electronic data processing system if desired. In this case the electrical control signals are generated in response to programmed in structions. The printer may also be operated as a standalone unit, in which case the printer would have its own control circuitry built in to cycle the machine through the desired steps to perform the printing functions of the machine. An operator oriented printer may utilize manually actuated switches to generate some control signals.

The developer conveying apparatus comprises drum conveyor 18 which is mounted for rotation about an axis substantially perpendicular to the surface of drum 10. Drum conveyor 18 comprises a hollow cylinder having a closed rear wall. A front wall member 36 is fixed to a suitable support means 26 and a suitable seal member 28 is provided to prevent developer material from escaping between fixed wall member 36 and drum member 18. Drum conveyor member 118 is supported for rotation by suitable support means 27. Side enclosure members 23 are shaped to the contour of drum to prevent the developer material from flowing out to other parts of the printer. Drive means 32 is provided to rotate drum conveyor 18 in the direction of the arrow by frictional engagement with the outer surface of the drum.

Rail members are provided to mount the developer apparatus adjacent drum 10. The entire developer apparatus can be moved along rail members away from the photoconductor surface and this movement results in decoupling the drive to drive means 32. This coupling serves to prevent operation of the developer apparatus and the possible accidental dumping of the developer material while the developer apparatus is in the retracted position. A magnetic field producing means 30 is mounted in close proximity radially to drum conveyor 18.

As drum conveyor llt l is rotated the developer material in the reservoir portion 16 of the drum is moved into the influence of the magnetic field produced by magnetic field producing means 30. The developer material adheres to the inner surface 34 of the drum due to the force of the magnetic field on the ferromagnetic carrier and is conveyed upward as the drum rotates. When the developer material reaches a point near the top of the drum the developer material moves out of the influence of the magnetic field and drops to the inclined chute 20 under the influence of gravity. The flow of the developer material from chute 2th is restrained by a front wall portion 36 which forms a restricted flow area for flow of the developer material to the photoconductor surface. The material conveying rate of the conveyor lid is chosen sufficient so that a reservoir of developer material is always maintained upon chute 20 so that an even flow of developer is provided through the development zone between development electrode 24 and the photoconductor surface.

Any suitable means may be provided as magnetic field producing means 30. The preferred apparatus as shown in FIG. 3 comprises a series of ceramic permanent magnets 38 and a series of pole pieces 40 which provide a uniform magnetic field parallel to the rota tional direction of the drum of sufficient force to convey the developer material to cascade down chute 20 and through the development zone. The magnetic field producing means 30 could as well be an array of elec trornagnets; however, the cost and power requirement for maintaining the magnetic field in this manner provides a disadvantage to the use of this apparatus.

The embodiment described above is suitable for the high speed operation required by an electrostatic printer which produces copy at a high output rate in the range of several thousand lines per minute. However, some operational requirements of the printer may require a closer control over the developer material to provide adequate operation. One such requirement is that a printer be capable of producing output copy on all standard size forms. For example, there are eleven standard width forms the width of which extends from 4 inches to 14 7; inches. It has been found that it is desirable not to cascade developer material over the area of the photoconductor drum which is not to be used for the production of images since this adds greatly to the cleaning requirement for the photoconductor surface. The surface of the photoconductor is generally subject to wear due to abrasion, so this selective flow operation also extends the usable life of the photoconductor.

To provide operation to control the flow of the developer material to only a selected part of the width of the photoconductor drum, selectively actuable magnet means 42 are provided to more closely control the distribution of the developer across the drum surface. The selectively actuable magnet means comprise electromagnets mounted closely adjacent to the outer surface of the drum 18 so that the magnetic field acts to hold the developer material to the inner surface ofthe drum. Thus, it can be seen that by energizing segments 44A by suitable signals on leads 45A from control means 25, the developer material can be conveyed to the right side (FIG. 6) of chute 20. The energization of magnetic segments 44A and 4413 results in the flow of developer material across the center part of chute 20. In the same manner, actuation of magnetic segments 44A, 44B and 44C results in the placement of developer material on the left end of chute 20.

Thus, by selective actuation of selected ones of magnetic segments 44A, 44B, 44C, the position that the developer material flows on chute 20 can be selectively controlled. it can also be seen that by selecting a pattern of magnetic segments 44A, 44B and 44C the distribution of the developer mixture can be evenly spread over the chute 20. The cross-mixing of the developer can also be promoted by selectively advancing the energization of magnetic segments 44 in a predetermined manner.

In some cases, it is desirable to cut off the flow of developer completely, such as, for example, when the printer is on a standby operational basis, since this provides the advantage of reducing the wear on the photoconductor surface as well as the developer material. The embodiment of the invention shown in FIG. 6 shows a selectively actuable magnetic array 46 for controlling the flow of developer material. Magnetic array 46 comprises a plurality of electromagnets mounted so that the magnetic field produced acts to attract the developer flowing down chute 20 through the gap produced by front closure 36. The attraction of the developer material stops the flow of the developer material upon energization of magnet array 46. The flow of developer material is restored in a fraction of a second so that the printer can be selectively operated in a relatively short time. If the operation of the printer requires the production of output copy on a variety of form widths, magnetic array 46 may be utilized to selectively flow developer material over only one selected part of the photoconductor drum. As previously mentioned, there are eleven standard form widths 4 extending from less than five to about fifteen inches in width. While it would be theoretically possible to provide selectively operable gate magnets for each of the eleven standard widths, this would necessitate the use of a relatively large number of magnets that would be closely spaced in the developer apparatus. A more desirable approach is to provide six magnets for selective operation to provide flow of developer material to a predetermined area across the width of the drum. By the selection of the four outside magnets 46A, 46B, 46E, 46F to extend approximately seven inches, this would provide flow for the three narrow standard size forms. The two outside magnets 46A, 46F are to provide a width of ll 1% inches to provide the ability to process the five widths of forms between 8 k and 11 whereas the full width of the developer would provide flow for the three standard size forms from 12 to 14 "/8 inches in width. Thus, in this case the magnets are selectively operable in response to a NARROW signal from control means 25 to process the three narrow forms; MEDIUM signal to energize only the two outside magnets to process the five standard forms between 8 /2 and l l inches in width; whereas a WIDE signal would not energize any of the gate magnets so that the widths from 12 to 15 inches can be processed. The control signals for the form widths are specified either in the instruction when the printer is being utilized in connection with a data processing system, or by a manually selected device such as a push button operated by the operator in response to the requirement for a particular size form. It can be seen that the elements of the magnet array 46 can also be selected in any other way to provide a flow across the predetermined part of the photoconductor drum 10.

Thus, it can be seen that there is provided a developer conveying apparatus which fulfills the objective of providing a developer for a high-speed electrostatic printer. The developer conveying apparatus disclosed provides a more even flow of the developer, better cross mixing of the developer and selective control so that a wide variety of forms can be processed in a manner that reduces abrasion and wear to the photoconductor surface and the other components of the developer system.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in the form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. Printing apparatus for cascading ferromagnetic developer material across an electrophotographic surface for developing an image thereon and for recirculating the developer material for subsequent reuse comprising:

a hollow drum member adapted to hold the developer material mounted for rotation about an axis substantially perpendicular to the electrophotographic surface;

magnetic field producing means fixedly mounted adjacent the outer peripheral surface of said drum member for producing a magnetic field directed radially along a portion of the upward moving portion of said drum member;

a chute member mounted at an angle to the electrophotographic surface for directing the developer material to the surface; and

drive means for continuously rotating said drum member whereby said developer material is conveyed upwardly by being held to the inner peripheral surface of said drum member by said magnetic field and deposited on said chute member as the developer material moves out of the magnetic field to cascade across the electrophotographic surface to develop an image thereon.

2. The apparatus according to claim 1 wherein said magnetic field producing means comprises:

a plurality of magnetic pole pieces shaped to the curvature of said drum member; and

permanent magnet material mounted between said pole pieces to produce a magnetic field extending over a substantial width of said drum member.

3. The apparatus according to claim 2 wherein said magnetic field producing means presents a staggered a second selectively operable magnetic field producing means fixedly mounted adjacent to the outer peripheral surface of said drum member for selectively producing a magnetic field directed radially along the portion of said drum member above said first magnetic field producing means;

a chute member mounted at an angle to the electrophotographic surface for directing the developer material to the surface;

means for selectively energizing said second magnetic field producing means for directing the flow of developer material to a predetermined area of the electrophotographic surface; and

drive means for continuously rotating said drum member whereby said developer material is conveyed upwardly by being held to the inner peripheral surface of said drum member by said combined magnetic fields and deposited on said chute member as the developer material moves out of the magnetic fields to cascade across the predetermined area of the electrophotographic surface to develop an image thereon.

5. The apparatus according to claim 4 wherein said second magnetic field producing means comprises a plurality of electromagnets mounted adjacent the drum member; and

means for energizing selected ones of said electromagnets to direct the developer material to a predetermined area of the electrophotographic surface.

6. The apparatus according to claim 4 additionally comprising:

a plurality of selectively operable gating means mounted adjacent to said chute means to selectively limit the flow of developer material to the predetermined area of the electrophotographic surface; and

means for energizing selected ones of said electromagnets to direct the developer material to a predetermined area of the electrophotographic surface.

7. Printing apparatus for cascading ferromagnetic developer material across an electrophotographic surface for developing an image thereon and for recirculating the developer material for subsequent reuse comprising:

a hollow drum member adapted to hold the developer material mounted for rotation about an axis substantially perpendicular to the electrophotographic surface;

magnetic field producing means fixedly mounted adjacent the outer peripheral surface of said drum member for producing a magnetic field directed raidally along a portion of the upward moving portion of said drum member;

a chute member mounted at an angle to the electrophotographic surface for directing the developer material to the surface;

a plurality of selectively operable gating means mounted adjacent to said chute means to selectively limit the flow of developer material to a predetermined area ofsaid chute member; and

drive means for continuously rotating said drum member whereby said developer material is conveyed upwardly by being held to the inner peripheral surface of said drum member by said magnetic field and deposited on said chute member as the developer material moves out of the magnetic field to cascade across the electrophotographic surface to develop an image thereon.

8. The apparatus according to claim 7 wherein said gating means comprises:

a plurality of electromagnets mounted adjacent said chute member; and

means for energizing selected ones of said electromagnets to direct the developer material to a predetermined area of the electrophotographic surface.

9. Printing apparatus for cascading ferromagnetic developer material across an electrophotographic drum for developing an image thereon'and for recirculating the developer material for subsequent reuse comprising:

a hollow developer drum member adapted to hold the developer material;

means for supporting said hollow drum member adjacent an electrophotographic drum surface for rotation about an axis substantially perpendicular to the electrophotographic drum surface;

said developer drum member comprising a hollow cylinder having a wall at one end and having a first and a second opening in the other end wall;

a flow restricting member mounted on said other end wall extending between said first and said second openings to produce a flow path for said developer material closely adjacent to said electrophotographic drum surface;

a chute member mounted to said other end wall to direct the developer material through said first opening;

means to direct said developer material from said flow restricting member through said second opening to the lower part of said developer drum member;

magnetic field producing means fixedly mounted adjacent the outer peripheral surface of said developer drum member for producing a magnetic field directed along a portion of the upward moving portion of said developer drum member; and

drive means for continuously rotating said drum member whereby said developer material is conveyed upwardly by being held to the inner peripheral surface of said drum member by said magnetic field and deposited on said chute member as the developer material moves out of the magnetic field to cascade across the electrophotographic drum surface to develop an image thereon.

10. The apparatus according to claim 9 additionally comprising:

a second selectively operable magnetic field producing means fixedly mounted adjacent to the outer peripheral surface of said developer drum member for selectively producing a magnetic field direct along the portion of said developer drum member above said first magnetic field producing means; and

means for selectively energizing said second magnetic field producing means for directing the flow 12. The apparatus according to claim 10 additionally comprising:

a plurality of selectively operable gating means mounted to selectively limit the flow of developer material through the adjacent portion of said first opening. 

1. Printing apparatus for cascading ferromagnetic developer material across an electrophotographic surface for developing an image thereon and for recirculating the developer material for subsequent reuse comprising: a hollow drum member adapted to hold the developer material mounted for rotation about an axis substantially perpendicular to the electrophotographic surface; magnetic field producing means fixedly mounted adjacent the outer peripheral surface of said drum member for producing a magnetic field directed radially along a portion of the upward moving portion of said drum member; a chute member mounted at an angle to the electrophotographic surface for directing the developer material to the surface; and drive means for continuously rotating said drum member whereby said developer material is conveyed upwardly by being held to the inner peripheral surface of said drum member by said magnetic field and deposited on said chute member as the developer material moves out of the magnetic field to cascade across the electrophotograPhic surface to develop an image thereon.
 2. The apparatus according to claim 1 wherein said magnetic field producing means comprises: a plurality of magnetic pole pieces shaped to the curvature of said drum member; and permanent magnet material mounted between said pole pieces to produce a magnetic field extending over a substantial width of said drum member.
 3. The apparatus according to claim 2 wherein said magnetic field producing means presents a staggered magnetic field relative to the axis of said drum member.
 4. Printing apparatus for cascading ferromagnetic developer material across an electrophotographic surface for developing an image thereon and for recirculating the developer material for subsequent reuse comprising: a hollow drum member adapted to hold the developer material mounted for rotation about an axis substantially perpendicular to the electrophotographic surface; first magnetic field producing means fixedly mounted adjacent the outer peripheral surface of said drum member for producing a magnetic field directed radially along a portion of the upward moving portion of said drum member; a second selectively operable magnetic field producing means fixedly mounted adjacent to the outer peripheral surface of said drum member for selectively producing a magnetic field directed radially along the portion of said drum member above said first magnetic field producing means; a chute member mounted at an angle to the electrophotographic surface for directing the developer material to the surface; means for selectively energizing said second magnetic field producing means for directing the flow of developer material to a predetermined area of the electrophotographic surface; and drive means for continuously rotating said drum member whereby said developer material is conveyed upwardly by being held to the inner peripheral surface of said drum member by said combined magnetic fields and deposited on said chute member as the developer material moves out of the magnetic fields to cascade across the predetermined area of the electrophotographic surface to develop an image thereon.
 5. The apparatus according to claim 4 wherein said second magnetic field producing means comprises a plurality of electromagnets mounted adjacent the drum member; and means for energizing selected ones of said electromagnets to direct the developer material to a predetermined area of the electrophotographic surface.
 6. The apparatus according to claim 4 additionally comprising: a plurality of selectively operable gating means mounted adjacent to said chute means to selectively limit the flow of developer material to the predetermined area of the electrophotographic surface; and means for energizing selected ones of said electromagnets to direct the developer material to a predetermined area of the electrophotographic surface.
 7. Printing apparatus for cascading ferromagnetic developer material across an electrophotographic surface for developing an image thereon and for recirculating the developer material for subsequent reuse comprising: a hollow drum member adapted to hold the developer material mounted for rotation about an axis substantially perpendicular to the electrophotographic surface; magnetic field producing means fixedly mounted adjacent the outer peripheral surface of said drum member for producing a magnetic field directed raidally along a portion of the upward moving portion of said drum member; a chute member mounted at an angle to the electrophotographic surface for directing the developer material to the surface; a plurality of selectively operable gating means mounted adjacent to said chute means to selectively limit the flow of developer material to a predetermined area of said chute member; and drive means for continuously rotating said drum member whereby said developer material is conveyed upwardly by being held to the inner peripheral surface of said drum member by said magnetic field and deposited on said chute member as the developer material moves out of the magnetic field to cascade across the electrophotographic surface to develop an image thereon.
 8. The apparatus according to claim 7 wherein said gating means comprises: a plurality of electromagnets mounted adjacent said chute member; and means for energizing selected ones of said electromagnets to direct the developer material to a predetermined area of the electrophotographic surface.
 9. Printing apparatus for cascading ferromagnetic developer material across an electrophotographic drum for developing an image thereon and for recirculating the developer material for subsequent reuse comprising: a hollow developer drum member adapted to hold the developer material; means for supporting said hollow drum member adjacent an electrophotographic drum surface for rotation about an axis substantially perpendicular to the electrophotographic drum surface; said developer drum member comprising a hollow cylinder having a wall at one end and having a first and a second opening in the other end wall; a flow restricting member mounted on said other end wall extending between said first and said second openings to produce a flow path for said developer material closely adjacent to said electrophotographic drum surface; a chute member mounted to said other end wall to direct the developer material through said first opening; means to direct said developer material from said flow restricting member through said second opening to the lower part of said developer drum member; magnetic field producing means fixedly mounted adjacent the outer peripheral surface of said developer drum member for producing a magnetic field directed along a portion of the upward moving portion of said developer drum member; and drive means for continuously rotating said drum member whereby said developer material is conveyed upwardly by being held to the inner peripheral surface of said drum member by said magnetic field and deposited on said chute member as the developer material moves out of the magnetic field to cascade across the electrophotographic drum surface to develop an image thereon.
 10. The apparatus according to claim 9 additionally comprising: a second selectively operable magnetic field producing means fixedly mounted adjacent to the outer peripheral surface of said developer drum member for selectively producing a magnetic field direct along the portion of said developer drum member above said first magnetic field producing means; and means for selectively energizing said second magnetic field producing means for directing the flow of developer to a predetermined axial area of the electrophotographic drum surface.
 11. The apparatus according to claim 9 additionally comprising: a plurality of selectively operable gating means mounted to selectively limit the flow of developer material through the adjacent portion of said first opening.
 12. The apparatus according to claim 10 additionally comprising: a plurality of selectively operable gating means mounted to selectively limit the flow of developer material through the adjacent portion of said first opening. 